Early menarche predicts incidence of asthma in early adulthood.

The present study explores the effect of age at menarche on the incidence of asthma during early adulthood. The analysis was based on Canadian girls followed up from 8-11 to 18-21 years of age during the first 6 cycles (1994-2005) of the National Longitudinal Survey of Children and Youth. Early menarche was defined as 1 standard deviation less than the average age at menarche. Asthma occurrence after menarche was measured as asthma that was diagnosed by a health care professional. The authors used logistic regression to investigate the association between early menarche and incidence of asthma, adjusting for possible confounders. A total of 1,176 girls weighted to represent 352,345 Canadian girls were analyzed. The incidence of asthma after menarche was 11.2% (95% confidence interval: 8.3, 14.0). The onset of early menarche (<11.56 years of age) predicted postmenarcheal incidence of asthma; girls who matured early had more than twice the risk of developing asthma during early adulthood than did girls who matured at an average age (odds ratio, 2.34, 95% confidence interval: 1.19, 4.59). The present study provides partial insight into the worldwide rapid increase in asthma rates that coincides with the declining trends in menarcheal timing. Further studies within different contexts are warranted to assess the generalizability of these Canadian findings.